Apparatus for regulating combus



Dec. 12, 1950 c, MlLLER APPARATUS FOR REGULATING COMBUSTION IN SPREADERSTOKER FURNACES Filed Feb. 20, 1948 hvvewro/e 52/715 6. MILLER BY M WPatented Dec. 12, 1950 ermaerv ee UL I Compsrrou -lnsr-n napnn sroggnnensueons Earle, Millers Worcester, Mass assignor t nileytsiokrr G mqr m,W rces r, Mass corporation of Massachusetts Application February 20, 1913-,Serial No. 9,899 S CIaims, (Cl. 110 191 This invention relates. tooombustionaregul ation, and more particularly to an improved apparatusforregulatingcombustion in furnaces. of the spreader stokentype.

Dhe ordinary spreader stoker furnace includes amechanism which feedsfuel ata controlledirate to arotor or distributor locatediadjacent;ansopening: in awall of;thefurnacet The distributoris rotated, usuallyabouta horizontal axis, and. it is provided with blades which throw: thefuel through thewalLopeningand onto a grate within the furnacetomaintain a bed: of burning, fuel. Air-is supplied: for combustion, andthe finer particles of fuelburnin suspension, whereas the coarserparticles fall upon the fu l bed and: are thereconsumed;

'I-wogenera-b types of combustion control: are in common use.- Firstthere is the so-called "fioati-ng control, whereby the supplies of fueland air are variedf-ina smooth or gradual manner in accordance withvariations in the demand for heat,wi;thin a definite operatingrange.Second there is the so-called start-stop? control; whereby the suppliesof fuel and airare started and stopped in accordance with the variationsin the demand: for heat: Floating= contro1 pro vides more efficientoperation, since; the rate of combustion is maintained closely in stepwith the heat requirements, and. sudden changes in' combustionconditions are largelyavoided. The operating rang e howeveris morelimited, audit is diflioult to operate with such a control when thedemandfor heat isvery low. "Start-stop control is well adapted forinstallations in which a very. wide operating range is required, and inwhich the demand for heat may at times beat a minimum, However, thecombustion efficiency will be less, because of the sudden changes in;the combustion rate between zero. and the maximum. Furthermore, it isnotdesirable to stop the rotation of the stoker distributor; for when thisis done some of: the fuel may become wedged between the distributor andits housing: and thus prevent the distribu-tonfrom starting its rotationagain. Also, a stationary shaft. will be, heated from onesi'de only, andthis will cause distorticn of the'shaft.

It is accordingly one object of the invention to overcome thesediniculties andflto, provide an pparatus for regulating combustiou in aspr ader stokerfurnace which, will realize the advantagesof the-knowntypes oftcontiiol while avoid ns the disadvanta es thereof.

It is af-ur her abid -tor nvention t are: vide apparatus whereby eliminaion a 2; a p ader Stoker. u ac mayb re u ted as efficient, manner.throughout, a wide range oi; def mand for heat.

It is a further object of the invention 111 1211),- videz an apparatuswhereby the combustion a spreader stoker furnace may be regulatedmuto;matically in a thoroughly satisfactory manner even when the demandfoiyheat is very. low,

With these and other objects in view; as will be apparent to those,skilled in the art, the in; vention resides in the combination, of partsset forth in the specification and; covered by the claims appendedhereto.

Referring to the drawings illustrating one em,- bodiment of theinvention, and in. which likereference numerals indicate like parts, the"single figure is a somewhatv diagrammatic. side el'evatidh of a steamgenerating furnace fired by' a spreader Stoker and equipped withcombustion regulating apparatus.

The embodiment illustrated comprises a furnace Ill having a front wall acombustio'n chamber I Z, a grate l4, and'an ash pit bran chamber I 5beneath the gratefAtf'the' frdnt of the furnace there is provided theusual fire door I immediately above the grate, an 'uie stal ash door l1communicatingwith the ashpit""5. Afjuel admission opening is providediri'the wall I] above'the deer l6. spreade f'stolger or knownconstruction is mounted on the to Pr e i l th u h h o ning UL T istoke'rcomprises a distributor 22 rotatable about a horizontalaxisadjacent the openihQ'lQ a' ref ciprocable ram 23' above thedistributor tbff d e he to an h per Z4 in nota io to. .9:

ply fuel by amt to the .v T distributar 2' a he a 2% ar t driven i ,1 iina n r' i n le t i moto i Stok r s d udes 2i t l y m unt d e d o rbl 2.1whi h ca b m v d s a y th q is cf he ram 23 known manner between zeroand'aa max um- Wh n the arm 21 is in the min m indicated by thebrolgenline 28Xthelstrol e of the ram andthe rate of teed will he master aswhen the arm 'is in the position indicated by, the broken line ZSJthestroke of the ram and the rate of feed will be at a maximum. The 2-1; isbiased downwardly toward its lowermostor zero position by a weight 38.Air for combustion is supplied to the .ash pit tithroughaduct 32 y h m oa a 33 d i by a e ect is new 34. The air flow is controlled by a damperoc ed With the u t s de an 31 Thi rm saee i a mantis-wh m serves to biasthe damper toward its closed position.

The heat produced by the combustion of the fuel is utilized to generatesteam in a boiler 49 associated with the furnace ID. This boilercomprises the usual water tubes 4| located in the path of the hot gasesleaving the combustion chamber l2, and the usual steam delivery pipe 42.Upon leaving the boiler, the furnace gases flow through a duct 44 to astack or other draft producing device (not shown). Within the duct 44there is provided a damper 45 having an arm 46. This damper ispreferably controlled automatically in known manner to maintain apredetermined pressure, slightly below atmospheric, in the combustionchamber I2. For this purpose there is shown a regulator 48 of the typedisclosed in the United States patent to Temple No. 1,992,048, grantedFebruary 19, 1935. This regulator comprises a pilot valve mechanism 49supplied with a suitable fluid under pressure through a pipe 50 andconnected by tubes 52 to a hydraulic motor 53. This motor is connectedto the damper arm 46 by a rod 54. The regulator 49 is connected to thecombustion chamber [2 by a pipe 55.

The fuel feed and the flow of combustion air are controlledautomatically in accordance with variations inthe demand for steam fromthe boiler 40. For this purpose there is provided an automatic regulator51 of the type disclosed in the United States patent to Temple No.2,049,549 granted August 4, 1936. This regulator comprises a diaphragmchamber 58 and a reversible motor 59. nected by a pipe 6| to the steamdelivery pipe 42, and the motor 59 is connected by a rod 62 to a lever63. A flexible cable 65 leads from the lever 63 over an idler sheave 66to the damper arm 31. A second flexible cable 68 leads from the lever 63over an idler sheave 69, thence in the form of a loop beneath an idlersheave 19, and thence over idler sheaves H and 12 to the fuel feedcontrol arm 21. The construction is such that with the idler sheave 1!!in the position shown in full lines, a full stroke of the regulator 51will move the arm 21 through the angle A between the broken line 29 anda broken line 13 which lies at an angle B with the broken line 28. Theangle A is preferably considerably greater than the angle B. As the arm21 is moved from the position 29 to the position 13, the damper 36 willbe moved from an open position to'a nearly closed position, maintainingthe proper ratio between the supplies of fuel and air at all times. Theautomatic control throughout the angle A will take place in a smoothlygraduated or floating manner, and it will correspond to a definite rangeof heat demand as indicated by the steam pressure transmitted throughthe pipe 6| to the regulator diaphragm chamber 58. Thus, by way of example, the maximum load position 29 may correspond to a steam pressureof say 200 pounds per square inch, and the position 13 may correspond toa steam pressure of say 208 pounds. While the steam pressure is at avalue between these limits, the regulator 51 will hold the feed controlarm 21 at a corresponding intermediate position.

If now the demand for heat should become so low as to cause the steampressure to rise ap preciably above 208 pounds (say to 210 pounds)requiring even less fuel than is represented by the arm position 13, afurther regulating means The diaphragm chamber 58 is conwill assumecontrol to stop the fuel feed and the fan 33. For this purpose certainadditional regulating apparatus is provided. Thus the idler sheave 10 ismounted on a yoke 15 which may be moved vertically by a reversiblehydraulic motor 15 connected by tubes 11 to a valve mechanism 19, thelatter being supplied with a suitable fluid under pressure through apipe 99. A solenoid 8! is connected to the valve mechanism 19 to actuatethe same in a known manner, the arrangement being such that when thesolenoid is energized, fluid will be admitted to the upper end of themotor 18 to hold the sheave 19 in its lower or full line position. Upondeenergization of the solenoid, the motor 16 will raise the sheave 10 tothe broken line position, thus slackening the cable 68 sufliciently tolower the arm 21 to the zero feed line 28. A pressure actuated mastercontroller, such as a master switch 93 of the well-known mercury tubetype, is connected to the steam pressure pipe 65. This switch may beadjusted to open when the steam pressure increases to say 210 pounds,and to close when the steam pressure decreases to say 208 pounds. Thefan motor 34 is connected to a suitable source of electrical energy bymeans of a magnetic contactor having three normally open switches 86 andan actuating coil 81. is also provided a magnetic contactor having twonormally open switches 89 and 99, and an actuating coil 9|. To ensuremaintenance of fuel bed ignition during periods of low heat demand, aninterval timer 93 is provided having a switch 94 which is closed atpredetermined intervals by a small electric motor 95. In addition,- asource 91 of electrical energy is provided, with a manually operableswitch 98 to control the same.

The various electrical connections will now be described. The solenoid8| and the switch are connected in series across the source 91, ascontrolled by the switch 98. The pressure switch 83 and the coil 9! arelikewise connected'in series across the source 91, and the switch 89 andthe coil 81 are similarly connected in series. The switch 94 isconnected in parallel with the switch 90. The motor 95 is connectedacross the source 91, as controlled by the switch 98.

The operation of the invention will now be ap-, parent from the abovedisclosure. The switch 98 will be closed, and if the steam pressure isless than 208 pounds the'master pressure switch 83 will be closed,energizing the coil 9!, so that theswitches 89 and 99 will be closed.The closed switch 89 will energize the coil 81, so the switches 86 willbe closed and the fan motor 34 will bein operation to drive the fan 33.The closed switch 99 will energize the solenoid 8|, so that the valve 19will cause the hydraulic motor 16 to hold the idler sheave 19 in itslower or full line position. The motor 95 of the interval timer 93 willclose the switch 94 periodically, but this will have no effect so longas the switch 90 is closed. The stoker motor 26 will operate con-'bustion gases will generate steam in the boiler 40, and the gases willthen escape at reduced temperature through the duct 44. The regulator 49will control the damper 45 in known man- There ner'toimaintain apredetermined sub-atmospheric pressure in the combustion chamber l2. Thesteam will flow through the pipe ezto a place of use. Anyincrease in thedemandlfor steam will tendtoreduce the-steam pressure, and vice versa.So long as the steam pressure remains within the operating range of theregulator 51, which we have assumed to. be from 200 to 208 pounds, thisregulator will control the fuel feed control armZl. and the airoontroldamper 36 in asmooth or-floating manner. In other words, these partswill assumepositions varying with the steam pressure, the position ofthe arm 21 being somewhere between the lines 23 and 713.

If now the demand for steam decreases until the steam pressure rises toZ'iidpounds, the regulator motor 59 will be at the upper limit of itsstroke, the damper 36 will benearly closed, and the stoker arm 21 willbe in the position indicated by the line i3, so that the ram 23 willfeed fuel at a lowrate to the distributor. If the steam pressurecontinues to increase and reaches 210 pounds, the master switch it willopen, deenergizing the coil 9!, and opening the switches se and 99.Opening the switch as will deenergize the coilai' and thus open theswitches 85, so that the motor 34 and the fan 33 will come to a stop.Opening the switch 93 will deenergize the solenoid 8!, causing the valve'59 to admit pressure fluid to the lower end of the motor '16, and thesheave 'lii will accordingly be raised to the broken line position. Thiswill slacken the cable i8 and lower the arm 21 to the position indicatedby the line 28, so that the stroke of the ram will be reducedsubstantially to zero. While the steam pressure remains above 208pounds, the periodic closing of the switch 94 by the motor 95, say fortwo minutes out of every ten minutes, will energize the solenoid 8i andcause the sheave E0 to return to its full line position, moving the arm2'17 to the line 13 position, and supplying a small amount of fuel tothe grate M. This will ensure the maintenance of ignition in the fuelbed during long periods of low demand for steam. When the steam pressuredecreases to 208 pounds, the master switch 33 will close, energizing thecoil 9!, and closing the switches es and The closed switch 89 willenergize the coil 8?, closing the switches as and starting the fan motor34 and the fan 33. The closed switch 98 will energize the solenoid 8!,causing the motor '56 to lower th sheave iii and raise the fuel feed armto the line 13 position. Thus the rate of combustion will be increased,tending to raise the steam pressure once more.

It will accordingly be seen that unless the demand for steam is verylow, the combustion will be under the control of the regulator 51, andthis regulator will operate in a floating manner to change the fuel andair supplies smoothly and gradually in accordance with variations in thesteam pressure. Under conditions of very low demand for steam, themaster switch 83 will be in control, starting and stopping the fuel feedand the forced draft fan as required to meet the steam requirements.Furthermore, if the demand for steam is low or even zero, the intervaltimer 93 will bring about an intermittent feed of fuel in amountssufficient to maintain ignition in the fuel bed, the necessary airflowing past the nearly closed damper 35 by reason of the slight suctionin the combustion chamber l2.

The invention makes it possible to operate the furnace automaticaly andefliciently over a very wide range of demand, in fact from zero demandup tothemaximumfuel burning capacity of the apparatus. Since thedistributor 22 is rotated continuously, even understart-stop control,there of the fuel feed control arm 2:? corresponds to a relatively lowrange in steam pressure and to a relatively high range in demandiforheat. Similarly, the angular movement 13 corresponds to arelatively'high range in steam pressure and to arelatively low range indemand for heat.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1, In combination with a furnace for the combust/ion offuel and theproduction of heat, a rotatable spreader 'stoker distributor to supplyfuel tothe furnace, means to continuously rotate said distributor, meansto feed fuel to the distributor, a forced draft fan to supply air to thefurnace, master controller responsive to changes in the demand heat, andconnections from the controller to the fuel feedingmeans and the fan,effective to start and stop the fuelfeed and-the fan as the demand forheat increases and decreases while the distributor continues to rotate.

2. In combination with a furnace for the combustion of fuel and theproduction of heat, a rotatable spreader stoker distributor to supplyfuel to the furnace, means to continuously rotate said distributor,means to feed fuel to the distributor, a forced draft fan to supply airto the furnace, an air control damper operatively associated with thefan, a master controller responsive to changes in the demand for heatover a relatively low range, an automatic regulator responsive tochanges in the demand for heat over a relatively high range, connectionsfrom the controller to the fuel feeding means and the fan effective tostart and stop the fuel feed and the fan as the demand for heatincreases and decreases within the low range and while the distributorcontinues to rotate, and connections from the regulator to the fuelfeeding means and the damper effective to adjust the same as the demandfor heat varies within the high range.

3. In combination with a furnace for the combustion of fuel and thegeneration of vapor, a rotatable spreader stoker distributor to supplyfuel to the furnace, means to continuously rotate said distributor,means to feed fuel to the distributor, a forced draft fan to supply airto the furnace, an air control damper operatively associated with thefan, a master controller responsive to changes in the vapor pressureover a relatively high range, an automatic regulator responsive tochanges in the vapor pressure over a relatively low range, connectionsfrom the controller to the fuel feeding means and the fan effective tostart and stop the fuel feed and the fan as the vapor pressure decreasesand increases within the high range and while the distributor continuesto rotate, and connections from the regulator to the fuel feeding meansand the damper effective to adjust the same as the vapor pressure varieswithin the low range.

i. In combination with a furnace for the combustion of fuel and thegeneration of vapor, a rotatable spreader stoker distributor to supplyfuel to the furnace, means to continuously rotate said distributor,means to feed fuel to the distributor, a forced draft fan to supply airto the furnace,

7 an electric motor to drive the fan, an air control damper operativelyassociated with the fan, a master pressure switch responsive to changesin the vapor pressure over a relatively high range,

- a first reversible motor controlled by the switch and movable througha predetermined stroke, an automatic regulator responsive to changes inthe vapor pressure over, a relatively 'low range and including a secondreversible motor movable through a predetermined stroke, connectionsfrom the second reversible motor to the damper to adjust the same,connections from the second reversible motor to the fuel feeding meansto adjust the same between a high feeding position and a low feedingposition, means connecting the first reversible motor tothe lastmentioned connections to adjust the fuel feeding means between the saidlow feeding position and a zero feeding position, and connections fromthe master pressure switch to the fan motor to start and stop the sameas the vapor pressure reaches respectively the lower and upper limits ofthe said" high range.

5. In combination with a furnace for thecombustion of fuel and theproduction of heat, a rotatable spreader stoker distributor to. supplyfuel to the furnace, means to continuously rotate decreases within thelow range and whilethe distributor continues to rotate, and connectionsfrom the regulator to the fuel feeding means eilective to adjust thefuel feed as the demand for heat varies within the high range.

' EARLE C. MILLER.

REFERENCES CITED The-following references are of record in the file ofthis patent:

v UNITED STATES PATENTS ,Number Name Date 1,472,280, Ousdahl Oct. 30,1923 2,055,641 Young Sept. 29, 1936 2,205,494 Schindler June 25, 19402,376,701 Klinker May 22, 1945 2,385,811 Hotchkiss Oct. 2, 1945

